Captain Math on Netflix

On a secret private forum I’m on, one of the members made a reference to the value of the $9.99/month plan at Netflix, where you can get 12-15 DVDs in the mail each month for that money. When this happens, I hear Captain Math in the corner, tsking away, so I ask him what he has to say. He says:

You’d have a hard time getting that many turn-arounds on the 9.99/month version, which only allows you one disk at a time. Even if you Netflix doesn’t impose their slowdown on you, and even if all the films you want are at the nearest Netflix warehouse, here are the turnarounds:

Put disk in mail: New disk arrives: Days between:
Monday Wednesday 2
Tuesday Thursday 2
Wednesday Friday 2
Thursday Saturday 2
Friday Tuesday 4
Saturday Tuesday 3
Sunday Wednesday 3

So on average, one is waiting 2.57 days between shipping off the disk and receiving the next one…. or it would be, but if you’re working the system to the limit (i.e., you’re staying at home, and you get the mail earlier enough in the day to watch the disk and put it out in the same day’s outgoing mail), some weird things happen (and for ease of tracking, we’re going to suppose no postal holidays to slow things down). You see, you’re never putting a disk in the mail on Sunday or Monday, because disks don’t arrive on Sunday or Monday (for those looking on at home: Netflix is closed on Saturdays, so they’re never shipping them out locally for Monday delivery). And since you only get disks on Wednesday if you send them out on Sunday or Monday, the person working the system to the limit won’t be sending them on Wednesday, either. And if you don’t send one out on Wednesday, you’ll never get one in on Friday. So what quickly happens is that you will be in a three-disk-a-week cycle – Tuesday, Thursday, Saturday. Under that, even in a 31 day month, you can never hit 15 disks. At most (on a month that starts on a Tuesday or Thursday) you’ll hit 14.
The moment you start to deal with the real world – people with jobs putting disks in the mail the day after they get them, that figure drops noticably.

He starts to reel off the turnarounds for people who watched their disks the night that they get them and return them the next day, but I point out that he’s delving into far more detail than anyone cares about on a topic that is trivial even to the folks involved in the discussion. At that, he says “then I have done my job!” and flies off.

Published in: on September 2, 2006 at 7:41 pm  Leave a Comment  

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